import java.util.Scanner;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: Microsoft
 * Date: 2023-02-03
 * Time: 22:49
 */

public class Main{
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        double d = scanner.nextDouble();
        double left = -10000f;
        double right = 10000f;
        while(right - left < 1e-8) {
            double mid = (left + right) / 2;
            if(mid*mid*mid < d) {
                left = mid;
            }else {
                right = mid;
            }
        }
        System.out.printf("%.6f",left);
    }
}





//public class Main {
//    public static void main(String[] args) {
//        Scanner scanner = new Scanner(System.in);
//        int n , q;
//        n = scanner.nextInt();
//        q = scanner.nextInt();
//        int[] arr = new int[n];
//        for (int i = 0; i < n ; i++) {
//            arr[i] = scanner.nextInt();
//        }
//        while (q-- != 0) {
//            int x = scanner.nextInt();
//
//            int l = 0,r = n - 1;
//            while(l < r){
//                int mid = (l + r) / 2;
//                if(arr[mid] >= x) r = mid;
//                else l = mid + 1;
//            }
//            if(arr[l] != x){
//                System.out.println("-1 -1");
//            }else {
//                System.out.print(l + " ");
//                l = 0;
//                r = n - 1;
//                while (l < r) {
//                    int mid = (l + r + 1) / 2;
//                    if (arr[mid] <= x) l = mid;
//                    else r = mid - 1;
//                }
//                System.out.println(l);
//            }
//        }
//    }
//}
